Messages in this thread | | | From | "Adam Kropelin" <> | Subject | Re: [linux-usb-devel] [PATCH] hiddev: output reports are dropped when HIDIOCSREPORT is called in short succession | Date | Mon, 22 Aug 2005 08:44:14 -0400 |
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Stefan Nickl wrote: > Hi, > > when trying to make the hiddev driver issue several Set_Report control > transfers to a custom device with 2.6.13-rc6, only the first transfer > in a row is carried out, while others immediately following it are > silently dropped. > > This happens where hid_submit_report() (in hid-core.c) tests for > HID_CTRL_RUNNING, which seems to be still set because the first > transfer is not finished yet. > > As a workaround, inserting a delay between the two calls to > ioctl(HIDIOCSREPORT) in userspace "solves" the problem. > The straightforward fix is to add a call to hid_wait_io() to the > implementation of HIDIOCSREPORT (in hiddev.c), just like for > HIDIOCGREPORT. Works fine for me.
Yup, I've seen the same issue on the apcupsd project. I added the hid_wait_io() call to HIDIOCGREPORT a while back since it used to suffer from the same problem. I'd have no objection to making HIDIOCSREPORT synchronous as well.
--Adam
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